Ethernet is basically a broadcast protocol. Its main advantage is its simplicity. This allows Ethernet to be implemented with less costly hardware and software. Ethernet has become a common protocol for local area networks. For purposes of this application, the term “Ethernet” includes the entire class of Carrier Sense Multiple Access/Collision Detection (CSMA/CD) protocols covered by the family of computer industry standards known variously as IEEE-802.3 and ISO 8802/3. This includes but is not limited to 1-Mb Ethernet, known as “StarLAN”, 10-Mb Ethernet, 100-Mb Ethernet, known as “Fast Ethernet”, 1-Gb Ethernet and any future CSMA/CD protocols at any other data rates.
Ethernet, as with other network protocols, transmits data across a packet switched network. In packet switched networks data is divided into small pieces called packets that are multiplexed onto high capacity inter-machine connections. Packet switching is used by virtually all computer interconnections because of its efficiency in data transmissions. Packet switched networks use bandwidth on a circuit as needed, allowing other transmissions to pass through the lines in the interim.
A packet is a block of data together with appropriate identification information necessary for routing and delivery to its destination. The packet includes a source address, a destination address, the data being transmitted, and a series of data integrity bits commonly referred to as a cyclical redundancy check or CRC. The source address identifies a device that originated the packet and the destination address identifies a device to which the packet is to be transmitted over the network.
As is known in the art, transmission of a data packet on a packet switched network results in a transmission burst which entails synchronously transmitting all bytes which make up the data packet.
In simple point-to-point networks having only an origin node and a destination node, idle bytes can be inserted between packets. In more complex multi-node networks, a link between nodes “i” and “j” is frequently left silent when there is nothing to be transmitted from node “i” to node “j”.
A data packet being transmitted on a 1 Gb Ethernet network has a capacity of a certain maximum number of bytes corresponding to the network bandwidth capacity, but usually a fewer number of bytes are transmitted.
An Ethernet packet size typically ranges from 40 to about 1500 bytes. A transmission rate of data communicated on the 1 Gb Ethernet network is typically less than about 600 Mbps; and is frequently not delay sensitive. Moreover, 1 Gb Ethernet packet transmissions are generally “bursty”—that is, they comprise a series of short, high density bursts with idle bytes or silent periods dispersed between the bursts.
A main drawback with conventional Ethernet is that there are significant limitations on the physical distance that the network can cover. Gigabyte Ethernet networks as with other forms of Ethernet are typically found in relatively short distance Local Area Networks (LANs) and Metropolitan Area Networks (MANs).
Long distance networks such as Wide Area Networks (WANs) frequently comprise Switched Optical Networks (SONETs) and frequently utilize conventional communications protocols such as OC12, OC3, or OC1, hereinafter collectively referred to as OCnc. In SONETs there is no particular packet size requirement.
Where it is desired to communicate the Ethernet data packet from the LAN or MAN in a first location across the long distance network to the LAN or MAN in a second location, it is necessary to convert the Ethernet packet to a format suitable for transmission across the long distance network. Encapsulation protocols have been developed to allow Ethernet packets to be transmitted over longer distances. In such protocols, the entire Ethernet packet is placed within another type of packet which has its own header and includes additional addressing information, protocol information, etc., and which conforms to a format of the long distance network. Thus, in encapsulation techniques a size of an encapsulating packet must be larger than a size of an encapsulated packet. Currently known OC12 SONET/WAN systems have a bandwidth capacity of about 622 Mbps. On the other hand, 1 Gb Ethernet packets are, by definition, one gigabyte. Thus, in order to communicate a 1 Gb Ethernet packet on an OC12 network a technique other than data encapsulation is required.
The prior art includes many attempts to solve the problem of transmitting a large packet through an intervening smaller packet carrying network having multiple channels. This prior art includes the following U.S. patents.
U.S. Pat. No. 6,148,010 to Sutton et al., incorporated herein in its entirety by reference, discloses a method and apparatus for distributing and consolidating data packets onto multiple network interfaces using frame-based inverse multiplexing to parse high speed data into frames for placement onto lower speed networks.
U.S. Pat. No. 6,111,897 to Moon, incorporated herein in its entirety by reference, discloses a multiplexing/demultiplexing apparatus in a digital communication system with a variable frame structure and a method of controlling the same. The apparatus comprises a first FIFO unit for buffering data inputted at a fixed speed, a first write controller for outputting a first write address to the first FIFO unit in response to a first data input clock, a first read controller for outputting a first read address to the first FIFO unit in response to a first data output clock, a stuff/delete determination unit for generating stuff and delete indication signals, a multiplexer for multiplexing output data from the first FIFO unit to output frame data, a demultiplexer for demultiplexing the frame data from the multiplexer, a second write controller for generating a second write address in response to a write enable signal from the demultiplexer and a second data output clock, second read controller for generating a second read address in response to a second data input clock, a clock adjustment unit for outputting the second data input clock to the second read controller, and a second FIFO unit for storing output data from the demultiplexer in response to the second write address from the second write controller and outputting the stored data in response to the second read address from the second read controller.
U.S. Pat. Nos. 6,094,439 and 6,081,523 to Krishna et al., incorporated herein in their entirety by reference, disclose a Gigabit network node having a media access controller outputting packet data at Gigabit rates using multiple 100 MB/s physical layer links coupled to a physical interface having a data router to enable implementation of a Gigabit network using low cost data links. At least a portion of the packet data is selectively transmitted in a modified reconciliation layer onto the plurality of physical layer links.
U.S. Pat. No. 6,034,974 to Matsuoka et al., incorporated herein in its entirety by reference, discloses a channel-selection-type demultiplexing circuit capable of demultiplexing signals to a desired output port during bit demultiplexing, instead of simply demultiplexing the bits as in conventional devices; and which performs bit demultiplexing based on a frequency division clock after selecting the bit signals to be demultiplexed to the desired output port from the N-channel multiplexed signal stream based on channel selection information.
U.S. Pat. No. 5,970,067 to Sathe et al., incorporated herein in its entirety by reference, discloses an asynchronous transfer mode (ATM) inverse multiplexed communication system wherein a series of communication cells are multiplexed over a set of communication links. Each communication cell includes a framing bit of a predetermined framing bit stream for each communication link and a control channel bit of a control message for each communication link. Inbound communication cells from each communication link are aligned according to the corresponding framing bit stream. The control message specifies an ordered list of logical identifiers to indicate a multiplexed sequence of transfer of the communication cells over the communication links.
U.S. Pat. No. 5,680,400 to York, incorporated herein in its entirety by reference, discloses a high speed data transfer mechanism for transferring files from a transmission host across a data link to a receiver host. An input data stream is split into N separate substreams by packaging data into packets, which may be of different sizes. As data is packetized, each packet is sent and presented to a separate data transmitter. Data is sent to the array of transmitter in round-robin fashion such that the data is first presented to the first transmitter, then to the second transmitter, and so on until each transmitter has been sent a packet, then the first transmitter is sent another, and so on, until all data packets have been sent to a transmitter. A receiving side of the mechanism then initializes as many receivers as needed, or as many data receive substreams as are required using as many receivers as are available. A substream reassembly unit reassembles data packets into a final output stream.
U.S. Pat. No. 5,570,356 to Finney et al., incorporated herein in its entirety by reference, discloses a data communication system includes a phase splitting circuit to split a high speed parallel data word into a number of individual parallel data bytes, a byte multiplexor for each of the phases of a phase splitting circuit, encoding and serialization circuits for converting each byte to an encoded form suitable for serial transmission, transmitting each encoded byte across one of a number of serial transmission links to a receiving device where the data is deserialized and decoded to recover the original byte which is then synchronized by a byte synchronization circuit. The byte synchronization circuits are then coupled to a word synchronization circuit where the original high bandwidth data word is recovered and transmitted on an internal high speed parallel bus within the receiving device.
U.S. Pat. No. 5,544,161 to Bigham et al., incorporated herein in its entirety by reference, discloses a network having an architecture that distributes services over a greater serving area. A broadcast consolidation section receives broadband data from a plurality of information providers. The broadcast consolidation section combines the data streams from different information providers and outputs a consolidated signal onto a transport ring. The broadcast ring supplies the consolidated broadcast edit to a plurality of network hubs, each of which downloads the consolidated broadcast data, converts the data and transmits it by optical fiber to a plurality of local access nodes. Each local access node combines data with downstream traffic supplied by a backbone subnetwork. The combined signals are output from the local access nodes. Demultiplexers in the network hubs and the local access nodes perform processing on received data streams, assign identification values, and output on broadband channels or narrowband channels.
U.S. Pat. No. 5,293,378 to Shimizu, incorporated herein in its entirety by reference, discloses a packet transmission system wherein a packet can be transmitted at a high rate over a long transmission distance. Under the control of a transmission controller, a separating circuit divides a packet of a packet signal into six payloads to make six transmission frames and adds a start delimiter and an end delimiter to the first and last transmission frames, and four transmitters send out the six transmission frames in accordance with sequence numbers at a rate at which the signal can be transmitted by way of time division transmission lines. Under the control of a reception controller, four receivers receive the transmission frames, and a restoring circuit assembles the transmission frames back into the original packet signal in accordance with the sequence numbers and the delimiter information.
In spite of the numerous existing or published patents, there remains a need for a system that can reliably, economically and efficiently take a data packet from a larger bandwidth network and compress it to a size such that it can be transmitted on a first channel of a narrower bandwidth payload network; and, where necessary, supplement the bandwidth capacity of the first channel of the narrower bandwidth payload network by providing, on demand, access to payload capacity of a second channel of the narrower bandwidth payload network.